Objective     To compare the effects of antisense oligodeoxynucleotide (AS-ODN) and Ribavirin against respiratory syncytial virus (RSV) in mice.       Methods     BALB/c mice infected of RSV were nasally dropped with AS-ODN (0.2

0.4 mg) or Ribavirin (0.4

0.8 mg). Seventy-two hours after infection

pulmonary viral titer was detected by plaque forming experiment

pulmonary RSV N gene mRNA expression was assayed by RT-PCR

and viral protein was detected by immunohistochemistry. To represent respiratory tract inflammation and side-effect caused by AS-ODN or Ribavirin

leukocytes and the subgroup cells in bronchoalveolar lavage fluid (BALF) were counted and pulmonary histopathologic changes were examined.       Results     Pulmonary titer of mice treated with 0.2

0.4 mg AS-ODN or 0.8 mg Ribavirin decreased as compared with that of infected control mice

and the plaque forming inhibition ratio was 34.48%

46.75% and 23.02% respectively. AS-ODN (0.4 mg) inhibited the expressions of pulmonary RSV N gene mRNA and protein by 30.54% and 29.41% respectively. Ribavirin (0.4 mg) decreased RSV protein expression by 17.65%. Furthermore

AS-ODN and Ribavirin both at dose of 0.4 mg dramatically decreased total number of leukocytes in BALF

but did not significantly improve pulmonary histopathologic changes. The mice merely dropped with AS-ODN or Ribavirin both at dose of 0.4 mg appeared no visible pulmonary histopathologic changes.       Conclusion     AS-ODN shows more potent anti-RSV activity than Ribavirin in mice

and their application through nasal drop has no obvious noxious and side effects. So AS-ODN is an efficient and safe anti-RSV agent.